As is known, so-called "thermoforming" machines, fall into two quite separate classes depending upon their method of operation; firstly there are thermoforming machines which form and cut the sheet at separate workstations and secondly there are machines which form and cut the sheet at a single workstation. Such machines are used in the production of objects of thermoplastics material, e.g. "disposable" objects, from a sheet of hot pressed material.
This invention relates to an apparatus which falls into this second class, in that the shaping or forming of objects and their separation from the sheet of starting material is effected at a single workstation.
The state of the art for thermoforming apparatus incorporating a single forming station, separation from the initial sheet and subsequent removal from the press, is represented by conventional single station machines and those according to U.S. Pat. No. 4,560,339 which will be briefly described hereinafter with reference to FIGS. 1 to 13 of the accompanying drawings, in which:
FIG. 1 is a side view in diagrammatic form of a thermoforming machine having an upper male die and a single lower female mould shown in the open press position prior to forming;
FIG. 2 is a side view of the machine of FIG. 1 shown with the press closed during the forming stage;
FIG. 3 is a view similar to that shown in FIG. 2 with the press closed during the cutting stage;
FIG. 3a is a schematic view of a detail of FIG. 3 shown on an enlarged scale;
FIG. 4 is a side view of the machine of FIG. 3 shown with the press open after the formed object has been cut out but still remains in the press;
FIG. 5 is a similar view to that in FIG. 4 but at a subsequent stage in which the pressed object is removed from the female mould and removed from the pressing area to a stacking collector;
FIG. 6 is a side view of a variation of the machine shown in FIG. 5 having a multiple row of moulds which discharge in bulk to a separate stacker;
FIGS. 7 to 10 show diagrammatic views of another variation of the machine shown in FIG. 5, in which the pressed objects are removed from the pressing area by means of a suction plate which can be placed between the male and female parts of the press;
FIG. 11 diagrammatically illustrates a plate which can lift a plurality of articles pressed in a single pressing operation by suction, used in the machine according to FIGS. 7 to 10;
FIG. 12 diagrammatically illustrates a front view of a thermoforming machine having a single upper male die and a double lower female mould which moves alternately beneath the male die; and
FIG. 13 includes a diagram which illustrates the stages and opening/closing cycle times for a thermoforming press having a single female mould.
The thermoforming cycle in machines which carry out forming and cutting at a single workstation can be described schematically as follows.